boshra-pardaz/cache_tab

In-memory cache Erlang / Elixir library

In-memory cache application for Erlang / Elixir apps

cache_tab application is intended to proxy back-end operations for Key-Value insert, lookup and delete and maintain a cache of those Key-Values in-memory, to save back-end operations.

Operations are intended to be atomic between back-end and cache tables.

The lifetime of the cache object and the max size of the cache can be defined as table parameters to limit the size of the in-memory tables.

Building

cache_tab application can be build as follow:

make

It is a rebar-compatible OTP application. Alternatively, you can build it with rebar:

rebar get-deps compile

Usage

You can start the application with the command:

$ erl -pa ebin -pa deps/*/ebin
Erlang/OTP 18 [erts-7.1] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Eshell V7.1  (abort with ^G)
1> application:start(cache_tab).

Then, you can create a table for a specific type of data to cache. You can create several tables to separate your cached data. The following command will create a table named tab_name:

cache_tab:new(tab_name, [{life_time, Seconds}, {max_size, N}]).

The optional life_time option is used to define cache entry expiration. The optional max_size option is used to limit number of entries to add in cache.

You can insert data into the cache with:

cache_tab:insert(tab_name, <<"key">>, <<"value">>, fun() -> do_something() end).

Cache inserts are designed to be able to act as a proxy to backend insert. That's the purpose of the fun called as last parameter (do_something). Return of the fun is ignored, but if it crashes, cache will not be stored. If value did not change compared to previous insert, the fun will not be called, saving possibly unneeded write operations

You can also lookup data from the cache:

cache_tab:lookup(tab_name, <<"key">>, fun() -> read_value_if_not_cached() end).

The fun in last parameter is used to read and cache the value from your back-end if it is not already in cache.

It is expected to return either {ok, Value} or error.

You can delete entries from back-end and cache with command:

cache_tab:delete(tab_name, <<"key">>, fun() -> do_something() end),

Info command will report about the hits / misses to help you tune your cache size / lifetime parameters:

cache_tab:info(tab_name, Info).

Info parameter can be: size, ratio or all.

Development

Test

Unit test

You can run eunit test with the command:

$ make test